what is eto ?

I'm author of this sample.
I'm Japanese.

"eto gem" is library for Chinese Zodiac(Japanese Zodiac).
There are 12 animals, with one animal allocated to every year.

子 – rat / mouse
丑 – ox
寅 – tiger
卯 – hare / rabbit
辰 – dragon
巳 – serpent / snake
午 – horse
未 – sheep
申 – monkey
酉 – rooster / cock
戌 – dog
亥 – boar

https://www.thoughtco.com/j...

Thanks.

will you please do a program for prime by getting input from the user